Balsa -- Lightweight Wood Has Variety of Uses.

BRING UP THE TOPIC of balsa wood and you are likely to inspire some snickers.

Balsa is considered a lightweight among woods. While it is the lightest of the commercial hardwoods and unlikely to make anyone's top-10 list of fine cabinet woods, balsa has a long, proud history -- it was used in construction of the Allies' planes in World War II -- and is one of the most frequently imported woods to the United States. In World War I, balsa was used extensively in making life rafts and for packing armor plates for battleships. Because of its light weight and good insulating properties, it is still used as a packing material for highly finished materials.

Grows Fast, Dies Young

Balsa (Ochroma lagopus) grows in the West Indies, Central America and tropical South America. Ecuador contributes large supplies of balsa, as do the plantations of India, Indonesia and the Caribbean.

According to Albert Constantine in the book Know Your Woods, under favorable circumstances, balsa trees are ready for cutting when they are seven years old. The trees begin to deteriorate at 12 to 15 years of age. "Older trees often develop rot at the base and become worthless," Constantine adds.

Most of the balsa that is sold is the sapwood, which is white, off-white or oatmeal colored, sometimes with a light yellow or pink cast. The heartwood is pale brown.

Balsa's strength varies, say the editors of the book World Timbers, with its density. "Where strength is important, material should be selected on a density basis with reference to published strength figures. As a rough guide, commercial balsa of average density has from one-half to one-third the strength of spruce."

Used in Sea and Air

Balsa, while considered the softest and lightest of commercial timbers, is classified as a hardwood. Its uses include insulation and sound-absorption material, packing material, life-belts, water sports equipment, theater props and stage furniture.

"Balsa" is the Spanish name for raft. Constantine writes that balsa logs were used by natives of Central and South America for making rafts, boats and canoes. Today the buoyant wood is still used to make boats, life rafts and buoys.

The wood ranks as the most popular wood used in making model airplanes designed to fly because the wood is light and strong but also easy to work.